Align import integration fixture with supported ESLint versions

[2nofa11]

Tell us about your environment

• ESLint version: N/A (integration fixture currently uses ^7.0.0)
• eslint-plugin-vue version: 10.4.0
• Vue version: N/A
• Node version: CI matrix (18/20/21/LTS)

The problem you want to solve.
The integration test fixture at tests/integrations/eslint-plugin-import installs ESLint v7, but this plugin supports ESLint ^8 || ^9.
Additionally, I wish to address the issue causing the CI to fail in #2916.

Your take on the correct solution to problem.
Bump the fixture dependencies to:

• eslint: ^9
• eslint-plugin-import: ^2.31.0

Test-only change; no user-facing behavior change.

Additional context